1. Field of the Invention
This invention relates to an improved system for chilling drinking water, the system being particularly suitable for cooling and dispensing bottled drinking water. Water cooling is preferably provided by a thermoelectric heat-transfer module that provides controlled ice block formation. The system is efficient, quiet and trouble-free as compared to compressor-type coolers.
2. Related Art
Due to concern over the quality of water from public systems, use of bottled water and water filters, and associated dispensers, is becoming more prevalent. Many individuals have realized the desirability of dispensing cooled rather than having only room temperature water. Various approaches have been utilized to cool the water.
For example, a conventional refrigerant circuit with a compressor, evaporator and condenser has been employed. Water in a dispenser has also been cooled with a thermoelectric module as disclosed in allowed U.S. patent application Ser. No. 08/250,364, now U.S. Pat. No. 5,501,077. Also, a cold sink, extending into a water tank, has been employed to transfer heat from the water to the thermoelectric module as disclosed in U.S. patent application Ser. No. 08/452,179, which is a continuation in part of the above-mentioned application. Heat is drawn from the water into a heat sink from which it is dissipated to the ambient environment. Preferably, an ice block forms on the cold sink and cools the water in the tank. Ice stores energy of the thermoelectric module to more efficiently cool an influx of warmer water.
PCT publication number WO93/08432 discloses a cooling dispenser having an ice producing means which comprises a thermoelectric module sandwiched between a cold side sink and a hot side sink. An infrared beam detects ice formation on the cold side sink, and when the ice formed grows large enough to block the beam, the cooling system is shut down and the ice is permitted to melt sufficiently to be dislodged from the cold side sink. The dislodged ice floats to the top of the tank and the system restarts to form more ice. The upper surface of the cold side sink is preferably concave with smoothly tapered sides so that the ice will release easily therefrom when the cooling system is shut down.
Several problems exist with water dispensers that employ ice block formation as the cooling medium. For example, it is sometimes difficult to control the dimensions of the ice block being formed. If the ice block extends outwardly enough to actually contact the dispenser spigot, the spigot can become plugged by ice. Also, fans used in chiller systems, including those used to cool the heat sinks, can generate unwanted noise. Another problem exists with chiller systems utilizing fans in that where such fans are allowed to operate at or near full speed conditions, noise generated as a result can be unwanted, is perhaps unnecessary and undesirable. In some systems, internal tank components cannot be removed to facilitate cleaning. Finally, although some water chilling dispensers provide for dispensing both chilled and unchilled water, this is accomplished through two separate valves, which may not be ideal aesthetically and does not permit pre-dispensing mixing of water of different temperatures.
Another problem relates to the formation of ice around either a vertically extending cooling probe assembly within the tank, where such a mechanism is used, or around a vertically extending cooling plate at the bottom of the tank. Room temperature or warmer water is most usually introduced at the top of the tank. Water in the lower portion of the tank is cooled adjacent the bottom of the tank. This temperature differential between the top and bottom areas of the tank causes convection currents, which can inhibit ice formation or make the ice forming process inefficient.